Hi, looking for some info on a Cat Twenty Two fuel tank, why the 2 tanks? Is it for a vapourising oil/petrol mixture...

Someone will correct me if I am wrong, simple answer, but back in the day, Kerosene was cheaper than gasoline, however, it was quite a bit harder to start an engine with kersosene,(higher ignition temp) than it was gasoline(lower ignition point). So the small tank was for gasoline, to start and warm up the engine. And the bigger tank was for cheaper kerosine . When the engine reached working temp, you switched from gas to kerosene.

that is exactly what i did on my R2--that was back in the 1960's

The small tank also makes a good backup if you run the big tank dry a mile from your truck. All of my early motor cycles were like that and you ran until it died and then changed the valve and headed for a fuel supply. Just dont let the fuel in the small tank go unused for too long.

power kerosene had more ommph in it than petrol of the day thanks to the oil content(the boosters and other additives didnt exist neither did hydrocracking). but needs heat to get it to light properly. so yes they would start on petrol which is more volatile and burned hot to heat the engine which once warm was changed over. also the original target product of oil refining was kerosene for lighting and other purposes petrol was considered waste product.

you can make something close to power kero by getting jet-A and adding 2 stroke oil to it. cant remember the ratio. not worth the hassle. when you can use products like flash lube mixed with normal petrol and get good performance. i have found it seems to be better with premium fuel in our stationary engines.